Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$82.42	7.850%	$88.89	$88.89	$88.90	$88.90
Purchase #2	$10.39	13.630%	$11.8062	$11.81	$11.80	$11.80
Purchase #3	$97.36	7.519%	$104.6805	$104.68	$104.70	$104.70
Purchase #4	$109.45	6.458%	$116.5183	$116.52	$116.50	$116.50
Purchase #5	$164.27	13.779%	$186.9048	$186.90	$186.90	$186.90
Purchase #6	$188.66	11.844%	$211.0049	$211.00	$211.00	$211.00
Purchase #7	$149.31	12.579%	$168.0917	$168.09	$168.10	$168.10
7 purchase totals =	$801.86		$887.8964	$887.89	$887.90	$887.90